Hello. I have been experimenting with xcomposite in xorg, to enable
transparency and other effects.
I added this to xorg.conf:

Section "Extensions"
Option "Composite" "Enable"
EndSection

and this under the Device section:
Option "RenderAccel" "true"
Option "AllowGLXWithComposite" "true"

Things are working fine. I can now call on xcompmgr and transset to enable
transparency on windows. However, things are incredibly slow. Only effect
that doesn't seem to cause a slowdown are the shadows and menu fading. All
the rest, pretty slow.
I'm running gnome 2.12 (with metacity), xorg-x11 6.8.2-r5, and nvidia
drivers (7676).
GLX seems to be working fine (I can run glxgears in composite enabled
server).
Also, I have experienced a few problems. Firefox window got fully
transparent somehow and I couldn't get it back. If I try to log out, the
dialog where it asks logout/restart/shutdown doesn't appear also.
gnome-panel goes to the back, and windows appear in front of them. Kinda
small bugs, but still bugs!
Has anyone managed to get it working fine and fast?

--
Bruno Lustosa, aka Lofofora | Email: bruno@lustosa.net
Network Administrator/Web Programmer | ICQ: 1406477
Rio de Janeiro - Brazil |